THE CANADIAN ENTOMOLOGIST. 



11. Chilosia alaskensis, Hunter.* 



Port Renfrew, July 3, 1901, and Glacier, July 20, 1901, R. C. 

 Osburn ; Vancouver, May 6, 1905, R. V. Harvey, and June 5, 1906, R. 

 S. Sherman. 



1 2. Chilosia pallipes, Loevv. 



Four specimens, all females, have the characters given by Loew for 

 the species, " humeri lutei, scutellum luteum " (Cent. Quarta, No. 70). 

 Glacier, Aug. 20, 1902, R. C. Osburn; Goldstream, July 19, 1904; and 

 Similkameen, July 20, 1906, R. V. Harvey. 



I must admit that I am not able to separate from this species by any 

 definite characters a much larger number of specimens, of which a 

 majority, and notably all the males, fall unquestionably into C. tristis, 

 Loew. Williston at one time placed tristis as a synonym oi pailipes (Syn. 

 N. A. Syrphidi^, p. 41)) but later retracted his statement {ibid, appendix, 

 p. 293). I am strongly inclined to the opinion that he was right in the 

 • first place, as the humeral and scutellar lutescent markings are extremely 

 variable in extent in my specimens, and in some cases are entirely 

 wanting. The legs also vary in the amount of yellow, and the shape of the 

 first posterior cell may show variation even between the two wings of the 

 same specimen. It is a very significant fact also that the male oi pailipes 

 has never been described. Pending more complete study of this question, 

 however, I enumerate the following under tristis : 



13. Chilosia tristis, Loew. 



Seventeen specimens in all taken as follows : Port Renfrew, July 6, 

 1901, and Field, July 19, 1901, R. C. Osburn; Goldstream, July 19, 1904; 

 Vancouver, Sept. 24, 1904, and Similkameen, July 20, 1906, R. V. 

 Harvey. Taken also at Kaslo, June 10 and July 2, 1903, R. P. Currie. 

 (Banff, Alberta, July 17, 1901, R. C. Osburn.) 



14. Chilosia iiigripejuiis, Williston. 



Port Renfrew, June 29, 1901, R. C. Osburn, and Vancouver, May 27, 

 1905, R. V. Harvey. 



*It is worthy of note that this species has recently been shown to be the 

 cause of the timber blemish known as " Black Check" in the Western Hemlock. 

 The young- larva enters an opening made in the bark by a tiny bark beetle 

 [Hylesimis sp.), and develops beneath the bark, forming- an unsightly scar. 

 Another species, C. hoodiana, attacks the White or Lowland Fir in the same 

 manner. These facts put a somewhat different economic aspect on the 

 Syrphidas as a whole, as they have hitherto been considered entirely harmless or 

 beneficial. For the work and interesting life-histories of these two Chilosias see 

 Circular Xo. 61, U. S. Dept. Ag-riculture, entitled " Black Check in the Western 

 Hemlock," by 'Sir. H. E. Burke. 



